DE69034169T2 - Method for accessing a multilayer optical disk - Google Patents

Description

BACKGROUND OF THE INVENTION

(1) Field of the invention

The The present invention relates to a method for accessing a desired Recording layer on a multilayer optical disk, having a plurality of recording layers.

(2) Description of the state of the technique

In recent years, the development of this type of optical disk has been greatly accelerated due to its large storage capacity and high access speed. To further increase the memory capacity, an optical disk as in 1 proposed.

This optical disk 12 includes three recording layers 8a to 8c formed of a photochromic material, such as spyropyrene, the layers being sandwiched between a pair of base plates 13 are arranged. These recording layers 8a to 8c have sensitivity peaks in the wavelengths λ ₁ to λ ₃ ( 2 ) while transmitting light of different wavelengths.

Data recording and playback are as described below. From a light source 9 , z. As a laser, light is emitted, which changes the wavelengths, and by means of a focusing optical system 10 focused in a very fine beam of light, whereupon the plate 12 is exposed with this light. The light passes through the recording layers 8a . 8b and 8c and is from a light detector 11 recorded in relation to the light source 9 located on the other side.

Now the data recording will be described in more detail. If that from the light source 9 emitted and onto the plate 12 Applied light has a wavelength λ ₂ , it is through the recording layers 8a and 8c passed through, but from the recording layer 8b absorbed, creating a data element 8b is recorded.

In data reproduction, only the data that is on the layer 8b recorded by exposure to a light beam of wavelength λ ₂ .

As becomes clear from the above, increases by creation of more recording layers the storage capacity.

If however, multiple recording layers are provided, increases the total thickness of the recording layers. To data on such thick plate single Lich by means of different wavelengths and without capturing the exact positions of the layers and reproduce, the light beam should be a fairly large diameter which prevents high density recording becomes.

Farther causes a beam of light with a large diameter overlay (cross-talks) between neighboring tracks.

Furthermore are other methods of recording and playing back data known.

The Japanese Patent Application JP-A-63 050 918 discloses a multilayered one optical plate open, in which different layers on light only a special wavelength speak to.

The British Patent Application GB-A-2 017 379 describes a conventional one multilayer optical disk with two recording layers, wherein each layer is provided on a respective base substrate. A transparent adhesive layer with a minimum thickness of 150 to 200 microns is located between the layers. By reflection and on the basis of occurring phase differences become the information of each Read layer.

The US patent application US 4,219,704 describes an improved reproducing apparatus having means for selectively accessing data stored on different layers of data within a multilayer optical disk.

The International Patent Application WO 89/02150 discloses a method for optionally accessing tracks of a disk with a single Data layer open, in which a number of tracks skipped can be and the number of tracks without pausing on each track counted exactly can be.

The European Patent Application EP-A-0 414 380 discloses a data reproducing apparatus with a multilayer optical disc open, creating transparent Plates of predetermined thickness exchangeable between an objective lens and the plate are arranged so that the focus of a laser for access can be changed to different layers of the plate.

SUMMARY THE INVENTION

Based on this, the present invention has the object, a multilayer optical Plat to detect a precise position of each recording layer so as to minimize the diameter of the light beam and thereby remarkably improve the recording density.

A Another object of the present invention is to provide a multilayer optical disk that overlays between adjacent ones Prevents traces and layers.

The above objects are achieved by a method of selectively accessing a desired recording layer on a multilayer optical disk, the multi-layer optical disk comprising:
a first recording layer applied to a first base plate;
a second recording layer applied to a second base plate;
at least one further recording layer disposed between the first layer and the second layer;
an undoped intermediate layer of an adhesive disposed between the first recording layer and the second recording layer, each recording layer having an identification portion, wherein information is recorded and / or reproduced on the recording layers by means of a focused light beam, the method comprising: reading the identifying portion of the layer on which the light beam is focused, using this read-out identifying portion to set this layer as a reference layer, changing the focus of the light beam, and detecting the zero crossing points of the S-curves of the respective focusing error signal, each S-curve of a respective recording layer corresponds until the same number of zero crossing points as the ordinal number of the desired recording layer is recognized, the ordinal number representing the number of recording layers, which are to be crossed in order to reach a desired layer starting from the reference layer and including it.

Of the Identification section can store an address of the track to which the identification section belongs.

The Traces of two layers adjacent in the thickness direction can be seen in FIG radial direction by half a track spacing be shifted from each other.

The Traces can each comprise a plurality of sectors.

The Sectors can each have an identification section containing the addresses the recording layer, the track and the sector to which the identification section belongs.

The Identification sections can be shifted against each other in the track direction.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention from the following description in conjunction with the attached Drawings clear, the specific embodiments of the invention represent. To the drawings:

1 Fig. 12 is a view showing the construction of a conventional multilayer optical disk together with a data recording and reproducing apparatus;

2 Fig. 16 is a view of a wavelength spectrum recorded on the above optical disk.

3 Fig. 12 is a vertical section through a first multilayer optical disk;

4 is a plan view of the optical disk 3 ;

5 FIG. 14 is a view of the structure of an identifying portion of the optical disk 3 ;

6 Figure 4 is a vertical section through a second multilayer optical disk;

7 is a plan view of the optical disk 6 ;

8th Fig. 12 is a vertical sectional view of a third multilayer optical disk according to the present invention;

9 is an enlarged view of a track 8th ;

and 10 Fig. 10 is a vertical section through a fourth multilayer optical disk according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

As in 3 shown comprises a first multilayer optical disk 1 an upper and a lower base plate 2 facing each other, a first recording layer 3 that lie on the bottom of the upper base plate 2 is a second recording layer 4 that are on the Top of the lower base plate 2 and an undoped interlayer 5 Made of a UV resin that prevents the recording layers 3 and 4 touching each other. The layers 3 and 4 have the well-known pit design.

As in 4 can be seen, include the recording layers 3 and 4 a multitude of concentric tracks 6a and 6b (for practical reasons, the tracks are in 4 shown in parallel). The traces 6a and 6b are shifted in the radial direction by half of a track pitch Pt against each other. Each track is divided into a plurality of sectors S, each of which has an identification section (for the track 6a as ID _a and for the track 6b ID _b ) and a data field DF for storing data. As in 5 1, each identification section ID _a and ID _b respectively comprise a section SYNC which synchronizes the clocks, an address marker AM indicating the beginning of an address signal, a track address TA, a sector address SA and a recording layer address LA.

The multilayer optical disk 1 is prepared by the recording layers 3 and 4 on the base plates 2 are formed with projecting portions and then the base plates 2 bonded together with an adhesive of a UV resin (the adhesive solidifies in the intermediate layer 5 ). Desirably, the intermediate layer 5 as thin as possible, but a thickness between 10 and 100 microns is acceptable. By the projecting portions, it is possible that the layers 3 and 4 each with pits (burn-in) are provided.

Data is as follows on the multilayer optical disk 1 recorded. First, a desired recording layer 3 or 4 called by the addresses LA of the recording layer of the disk 1 be reproduced. Second, a desired track 6a or 6b is called by reproducing the track addresses TA of the called layer. Third, the desired sector S is called by reproducing the sector addresses SA of the called track. Finally, a data item is recorded in the data field DF of the called sector S.

If a layer whose address is reproduced, not the one in the above first search operation Desired is, the following operation takes place to find the desired.

The light beam is defocused and onto the plate 1 applied while the position of the focus is changed. Every time the ray of light shifts 3 or 4 is traversed, an S-curve is generated indicating a focusing error. The zero crossing of each S curve is detected until it is determined that the number of zero crossings matches the ordinal number of the desired track. The atomic number is determined as follows: If the layer 4 the reference layer is, then the layer is 4 the first layer and the layer 3 is the second layer. Specifically, when the above number of zero crossings is detected, specifically, when the desired track is called, the light beam is refocused and the identification section ID _a or ID _b is read to confirm that the desired layer has been retrieved.

The desired track TA ₁ is retrieved as follows. When a track address TA _{2 is} reproduced, the position of TA _{2 is} compared with the position of the desired track address TA ₁ and the head of the light beam is moved by a linear motor until it reaches the desired track address TA ₁ (coarse search). When the desired track address TA _{1 is} confirmed, it advances to the next step in which the desired sector S is searched. If not, all track addresses TA ₂ are successively reproduced by the track seek actuator until the head reaches the desired track address TA ₁ (fine search).

The desired sector S is searched, in which the desired sector address SA ₁ and a read-out address are compared and in which the optical disc 1 until the head reaches the desired sector address SA ₁ . Data playback is the same as data recording.

Since the recording layers 3 and 4 Identification sections ID _a and ID _b comprising the addresses LA of the recording layers can be accurately detected on which layer and on which track the light beam is focused. Even if the number of recording layers is increased and thus the total thickness of the layers increases, high-precision recording and reproduction are performed. By providing a track address TA in each identification section, it is possible to easily confirm the desired track.

In addition, the tracks 6a and 6b shifted in the radial direction by half of the track pitch Pt against each other. In practical terms, therefore, the light beam never irradiates the adjacent recording layer, thereby largely preventing overlaps between adjacent identification sections and between adjacent data fields.

A second multilayer optical disk as shown in FIG 6 and 7 is differentiated from the first multilayer optical disk in that the identification portions ID _a and ID _{b are} slightly shifted from each other in the track direction. It is desirable if the identification sections ID _a and ID _b do not overlap when viewed from the radial direction. In addition to the advantages of the first multilayer optical disk, this construction further prevents the light beam from simultaneously impinging on adjacent identification portions, thus further limiting overlaps.

As in 8th shown comprises a third multilayer optical disk 1 according to an embodiment of the invention, three recording layers 7a to 7c , The layers 7a to 7c have identification sections ID _L1 , ID _L2 and ID _L3 . Furthermore, the layer has 7c Track / sector identification sections ID _TS identifying tracks and sectors. The traces of the layers 7a to 7c are not shifted, but aligned in the thickness direction. Each track / sector identification section ID _TS identifies a group of tracks and sectors aligned in the thickness direction. The layers 7a to 7c have the well-known pit design.

As in 9 ₁ , the track / sector identification section ID _{TS has} a pit pitch P ₁ , the identification sections ID _L1 , ID _L2 and ID _L3 have a pit pitch P _2, and the data field DF has a pit pitch P ₃ Pit distances in the ratio P ₁ > P ₂ = P ₃ to each other. Practically, P ₁ is set so that the recorded data can be reproduced sufficiently well when the light beam hits any of the layers 7a . 7b or 7c is focused (eg, P _{1 is} 5 μm or less). P ₂ and P ₃ are adjusted so that the recorded data are sufficiently well reproduced when the light beam is applied to the concrete layer 7a . 7b or 7c is focused (eg P ₂ and P _{3 are} each 0.8 microns). In other words, the track / sector identification section ID _TS can be read out when the light beam is focused on only one of the layers, while the identification sections ID _L1 , ID _L2 and ID _L3 can be read out when the light beam is focused on the concrete layer ,

How each layer is accessed, e.g. On the recording layer 7a , will be described below. In the present optical disk, the layer is 7c the reference layer, and the ordinal number of the layer 7a is known. The atomic number represents the number of recording layers that must be crossed in order to obtain a desired layer from and including the reference layer.

A beam of light is applied to the layer 7c focused when a specific number of zero crossings of the S-curves are detected as focus error signals, and the identification section ID _{L3 is} read out to confirm that the light beam is incident on the layer 7c is focused. When a certain number of zero crossings are detected, then the light beam is applied to the layer 7a focused. One obtains the certain number, by the atomic number of the layer 7a one is subtracted. The identification section ID _L1 is detected to confirm that the light beam is incident on the layer 7a is focused. Subsequently, the track / sector identification sections ID _TS are sequentially detected one by one until the desired track and then the desired sector are retrieved.

In the above construction, no further signal is generated in any of the portions of the layers 7a and 7b recorded, the portion perpendicular to the track / sector identification section ID _TS ; and the identification sections ID _L1 , ID _L2 and ID _L3 have pit intervals too small to be read unless the light beam is focused on the desired track. Therefore, in addition to the advantages of the first multilayer optical disk, the present third multilayer optical disk largely prevents overlays. Further, since it is not required that the tracks of the various layers are shifted by half the Sprur distance to each other, the productivity in the production of these optical disks increases.

Based on 10 Now, a fourth multilayer optical disk according to another embodiment of the present invention will be described. The same elements are marked with the same numerals as in the third multilayer optical disk, and therefore their explanation is omitted here.

This optical disk differs from the third multilayer optical disk in that the identification portions ID _L1 , ID _L2 and ID _{L3 are} slightly offset from each other in the track direction. Conveniently, the identification sections ID _L1 , ID _L2 and ID _L3 are removed by the distances T ₁ , T ₂ and T _3, respectively, from the track / sector identification section ID _TS . It is desirable, when T ₁ minus T ₂ or T ₂ minus T ₃ is equal to or greater than a length of _{IDL1, IDL2} and _L3 in the track direction. Since the identification sections ID _L1 , ID _L2 and ID _{L3 have the} same pit constructions as those of the third multilayer optical disk, the track / sector identification section ID _{TS can be} read out when the light beam is focused on only one of the layers while the identification sections ID _L1 , ID _L2 and ID _L3 can be read when the light beam is focused on the special layer. On the shift 7a can be accessed in the same way as the third multilayer optical disk.

In this optical disk, since the identification portions ID _L1 , ID _L2 and ID _L3 are shifted in the track direction from each other, the light beam is prevented from simultaneously exposing the adjacent identification portions. In addition to the advantages of the third multilayer optical disk, this present optical disk further restricts overlays.

Although in the above four multilayer optical disks, the tracks Sectors recorded on the entire tracks data.

at have the above examples of multilayer optical disks the recording layers sensitivity peaks in different wavelengths. Indeed The plate may have layers that are ordinary optomagnetic material are made, for. TbFeCo, or off a phase change material, e.g. B. GeSBTe. True, the present Invention based on embodiments with reference to the accompanying drawings, but of course for professionals different changes and modifications on hand. If such changes and modifications do not depart from the scope of the claims, However, it can be assumed that they fall into the same.

Claims (5)

A method of selectively accessing a desired recording layer on a multilayer optical disk, the multi-layer optical disk comprising: a first recording layer (16); 3 ; 7a ) placed on a first base plate ( 2 ) is applied; a second recording layer ( 4 ; 7c ) placed on a second baseplate ( 2 ) is applied; at least one further recording layer ( 7b ) between the first layer ( 7a ) and the second layer ( 7c ) is arranged; an undoped intermediate layer ( 5 ) of an adhesive which is between the first recording layer ( 3 ; 7a ) and the second recording layer ( 4 ; 7c ), each recording layer ( 3 ; 4 ; 7a ; 7b ; 7c ) has an identification section (ID _a , ID _b ), wherein information is conveyed by means of a focused light beam on the recording layers ( 3 ; 4 ; 7a ; 7b ; 7c ) and / or reproduced therefrom, the method comprising: reading the identification section (ID _a , ID _b ) of the layer on which the light beam is focused, using this read-out identification section (ID _a , ID _b ) to set this layer as a reference layer, changing the focus of the light beam and detecting the zero crossing points of the S-curves of the respective focus error signal, each S curve corresponding to a respective recording layer until the same number of zero crossing points as the ordinal number of the desired recording layer is detected the atomic number represents the number of recording layers to be crossed to reach a desired layer from and including the reference layer. Method according to claim 1, wherein the correct portion of the recording layer ( 3 ; 4 ; 7a ; 7b ; 7c ) is confirmed by reading one of its identification sections (ID _a , ID _b ) which stores the address of its recording layer. A method according to claim 1 or claim 2, wherein the undoped interlayer ( 5 ) has a thickness of 10 to 100 μm. Method according to one of the preceding claims, wherein the undoped intermediate layer ( 5 ) is formed from a UV resin. Method according to one of the preceding claims, wherein each of the recording layers ( 3 ; 4 ; 7a ; 7b ; 7c ) Traces ( 6a . 6b ) carrying recorded data, and wherein a signal for identifying a corresponding recording layer ( 3 ; 4 ; 7a ; 7b ; 7c ) on each track ( 6a . 6b ) is stored.